Nearly half a century ago Republican Presidential candidate Richard Nixon appropriated the phrase “silent majority” to characterize a broad swath of Americans who were white, worked hard, were not that well-educated, raised their families diligently, went to church on Sundays, and tried to live the post-war American dream.  But Richard Nixon's silent majority was also deeply worried about the major changes going on in 1960s America — notably the civil rights and anti-Vietnam war movements, the rise of the counter-culture, and the sexual revolution — that they felt threatened everything they believed in and valued about their country.In the 2016 presidential election a modern version of this segment of America spoke loud and clear.  This time, by contrast, they are a shrinking minority of Americans — which is one reason why they no longer remained silent, watching from the sidelines as 'their' America slips from their grasp.This silent minority of Americans has witnessed sweeping changes around them just like their forebearers experienced nearly two generations ago.  Today, the anxieties relate chiefly to disappearing jobs and eroding incomes from global competition and governments that seem unresponsive to these hardships, plus an aversion to the inexorable changing colour of America from white to brown.  These social, political and economic forces are seen by this group of people as threatening their very idea of America.  As a result, they came out on election day in sufficient numbers to put a demagogue in the White House.  And in so doing they took a huge risk for America and the world, far beyond anything their brethren did in electing Nixon in 1968.More than four decades ago the personification of the silent majority was Archie Bunker, the lead character from the sitcom All in the Family.  In an interview on CNN last week, Norman Lear, creator of All in the Family, suggested that he wasn't so sure the hard working, God-fearing, anti-feminist and racist Archie Bunker would vote for Donald Trump.  Lear implied that Trump in 2016 was probably too sexist for Bunker circa 1971.  That really says something about the turn America has taken in this election.For Canada this is a watershed moment.  Our political class have no idea how to deal with a Trump presidency — it was not in any realistic scenario being contemplated.  Up until now Canada has flown below Donald Trump's radar screen, unlike our Mexican friends and NAFTA partners, who have been one of his targets.  That is about to change as President-elect Trump is likely to be advised that his first foreign trip should be to this country, as is normal practice.There have of course been significant differences in policies, personalities and world views between Canadian and American political leaders in the past.  Lyndon Johnson and Lester Pearson did not get along.  Richard Nixon and Ronald Reagan presented real challenges for Pierre Trudeau in foreign and domestic policy alike, in both substance and tone.  As did Barack Obama for Stephen Harper.But the Donald Trump-Justin Trudeau gulf seems to be well beyond anything we have seen in living memory between an American President and a Canadian Prime Minister.  We have a septuagenarian, racist, chauvinist, business tycoon in the White House, versus a forty something, ultra-feminist, former school teacher Prime Minister who believes deeply that racial diversity and inclusion are Canada's greatest strengths.These are not policy differences that can be papered over or managed at the margins in the Canada-US relationship.  These represent sharp values cleavages.  Trump and his followers and Trudeau and his speak two different languages and come from different worlds.  Both men also see themselves as leaders of movements more than parties, and those movements could not be further apart in their thinking.  It's hard to imagine the twain ever really meeting.A few days go the conventional wisdom was that at the next general election in three years the Trudeau government would be defined on the basis of its environmental record, its ability to help the middle class, or perhaps its approach to aboriginals.  Today, by contrast, its more than likely that the defining feature of the Trudeau government will be its ability to manage its relationship with Donald Trump personally, his administration generally, and a broad range of bilateral files specifically — including trade, the environment, energy, immigration, national security and defence.This could be one of the most significant governing challenges any Canadian Prime Minister and Cabinet has faced.  Let's hope our leaders have the skills, the courage and the stomach for it.Eugene Lang is Adjunct Professor, School of Policy Studies, Queen's University.